Tetrapod Zoology

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If you said that the mystery duck from yesterday was a mallard, a weird mallard hybrid, a shoveler of some sort, or blah blah blah, then shame shame shame on you: you are a loser. If, however, you said it was a Meller’s duck Anas melleri, then well done, you are some kind of freakin’ duck genius, champion of your peers, wunderkid, and all round sterling human being. Yes, it was Meller’s duck, an endemic Madagascan species that inhabits the lakes, rivers, streams, ponds and wetlands of the eastern side of the central plateau, being associated in particular with Lac Alaotra (Madagascar’s largest lake) [adjacent Joseph Wolf illustration from wikipedia]. It also occurs on Mauritius, where the introduced population is said to be close to extinction (an introduction date of around 1850 was suggested by Meinertzhagen). An introduction attempt on Réunion was unsuccessful. So, well done Mo Hassan (of The Disillusioned Taxonomist), ObSciGuy (of The Obligate Scientist), Alan (of zoo volunteer), and John Harshman.

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The big giveaway is the proportionally long, blue-grey bill with its black nail (well done ObSciGuy Paul), though if you could see the green, white-bordered speculum (which you couldn’t…), it would help. Note also that a supercilium is absent, in contrast to the condition in mallards. In male Meller’s ducks, the two central tail feathers are longer than the other tail feathers, and are entirely black, whereas in females these central tail feathers are shorter and brown-edged (Young 1991). Males also tend to have longer heads and bills, and they also have black edges to the bill’s base (Lohan & Young 2004). This captive specimen – photographed at the Isle of Wight Tiger and Lemur Sanctuary – is the first and only one I’ve ever seen, and because I think I can see black edges to the bill base I reckon this is a male. It came to the Isle of Wight collection from Jersey Zoo, where a breeding population of about 230 birds have been reared from 13 individuals caught in the wild between 1994 and 2001 (Young 2005). There were apparently two birds in the enclosure but I could only see one. Anyway, I’m a big duck fan, so seeing a live specimen was a big deal for me. It was particularly frustrating to see an endless stream of zoo visitors take a quick look at it, announce frustration or puzzlement at the presence of a mallard in a zoo devoted to exciting tropical animals, and to walk off without any attempt at self-education (it’s not as if the sign wasn’t obvious: it’s shown below. You had to go to the trouble of rotating your head slightly to the left to see it).

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After being named as a new species in 1865*, Meller’s duck had a bit of a rocky ride. Its superficial similarity to the Mallard A. platyrhynchos has meant that various authors have regarded it as a mallard subspecies, or even just as a local variant and not even as a subspecies. These hypotheses went hand-in-hand with the widespread idea that the various non-dimorphic, mallard-like ducks of the world’s oceanic islands were simply the sedentary products of mallard migration: in other words that they were degenerate mallards. Viewed as simply a local mallard variant, Meller’s duck was not deemed to be worthy of conservation effort. Luckily, this idea was not accepted by everyone, and DNA sequencing has demonstrated that Meller’s duck belongs to a distinct lineage that does not fall into A. platyrhynchos (Young & Rhymer 1998). This view of distinct species status is consistent with the fact that it also exhibits behavioural and morphological autapomorphies (Young & Rhymer 1998, Young 1999).

* It’s named for Charles James Meller, the surgeon on David Livingstone’s East African expedition. Meller collected two of the ducks in 1862 but misidentified them as Red-billed pintails A. erythrorhyncha (Young & Rhymer 1998, Young 2005).

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Other non-dimorphic members of the mallard group – namely the Yellow-billed duck A. undulata and African black duck A. sparsa – appear basal relative to the Meller’s duck + mallard clade. An interesting consequence of this phylogenetic hypothesis is that the strong sexual dimorphism present in the mallard must (well, ‘must’) have evolved from a non-dimorphic condition, rather than the other way round. It has been hypothesised that absence of a dimorphic plumage (and hence an absence of an eclipse plumage) is advantageous for sedentary tropical and subtropical ducks, as it means that they’re able to breed whenever conditions are suitable; in contrast, sexual dichromatism works well in more predictable, seasonal habitats. Alternative hypotheses have posited that dull plumages have evolved in populations where parental investment from males is higher, that ‘isolating mechanisms’ have been lost as ‘confusable congeners’ no longer occur, or that monochromatism is paedomorphic and linked pleiotropically to paedomorphosis in the wing skeleton (see Livezey 1991). However, the last three hypotheses all assume that dichromatism is the primitive state and monochromatism is derived, rather than vice versa [adjacent pic shows captive Meller’s duck at Cologne Zoo, from wikipedia].

Meller’s duck is one of three waterfowl species endemic to Madasgascar: the others are the recently rediscovered Madagascar pochard Aythya innotata and the Madagascar or Bernier’s teal Anas bernieri (there is also an endemic subspecies of White backed duck, Thalassornis leuconotus insularis). Two additional Madagascan endemics – Greater Madagascan sheldgoose Centrornis majori and Lesser Madagascan sheldgoose Alopochen sirabensis – are extinct. Numerous other taxa occur (or occurred) in the region as well, and it seems that the western Indian Ocean was an important region in waterfowl biogeography. The human colonisation of the region resulted in the decline and extinction of many waterfowl populations. However, Madagascar seems to have become increasingly arid within the last millennium, and this may also have contributed to waterfowl decline (Young & Kear 2006).

For other Tet Zoo articles on ducks and other anseriforms see…

Refs – –

Livezey, B. C. 1991. A phylogenetic analysis and classification of recent dabbling ducks (Tribe Anatini) based on comparative morphology. The Auk 108, 471-507.

Lohan, C. & Young, H. G. 2004. Sexual dimorphism and individual variation in the bill markings of Meller’s duck, Anas melleri. Ostrich 75, 176-177.

Young, G. H. 1991. Sexual dimorphism in Meller’s duck Anas melleri. Bulletin of the British Ornithologists’ Club 111, 225-228.

– . 1999. Comparative study of the courtship displays of Meller’s duck Anas melleri, Yellowbilled duck A. undulata and Northern mallard A. platyrhynchos. Ostrich 70, 117-122.

– . 2005. Meller’s duck Anas melleri. In Kear, J. & Hulme, M. (eds) Bird Families of the World: Ducks, Geese and Swans. Vol. II. Oxford University Press, pp. 543-545.

– . & Kear, J. 2006. The rise and fall of wildfowl of the western Indian Ocean and Australasia. Bulletin of the British Ornithologists’ Club 126A, 25-39.

– . & Rhymer, J. M. 1998. Meller’s duck: a threatened species receives recognition at last. Biodiversity and Conservation 7, 1313-1323.

Comments

  1. #1 AnJaCo
    August 26, 2009

    Ha! Now I get the significance of the green bar over the wing of the original photo.

    Also, the picture of the sign at the zoo reminded me of the books by Gerald Durrell that I read many years ago. Great reads for young and old about the Joys of Natural History.

  2. #2 Mo Hassan
    August 26, 2009

    That really was too easy… even with the speculum hidden :p

    I first saw Meller’s ducks in Edinburgh Zoo 4 years ago, and there wasn’t even a sign. I knew they weren’t just mallards, so I trawled through the list of all the Anas ducks and found it. Luckily I did see the green speculum.

    I’ve never seen you mention any of the WWT centres, they always have loads of rare wildfowl and you don’t even have to like birdwatching. I can vouch for the London Wetland Centre being fantastic… dendrocygnids a-plenty! Should be going to Slimbridge when I’m down in Bristol for SVP.

  3. #3 Strider
    August 26, 2009

    When I was a kid my buddy and I “invented” the word ‘Meller’ and we thought it was a scream!

  4. #4 mus
    August 26, 2009

    On a COMPLETELY unrelated note (well, I guess ducks are pretty famous for having big ones), I have a question.

    I was reading an article which led me to start thinking about penises. Besides all the questions I have about the function of hooks among snake penises and whatnot, it struck me that I cannot think of a single nonhuman animal that has skin on its penis. All nonhuman animals I can think of at most have skin covering the flaccid penis, but the penis comes out when erect. Anyone know if there is a reason for this? Why are humans the only (or among the few) animals whose penis is covered with skin, which expands and continues to cover the shaft when erect?

  5. #5 Tim Morris
    August 27, 2009

    All very nice. I do have a soft spot for ducks.

    It’s obviously my greedy, profit minded illustrator side coming out, but I seem to fail when it comes to finding reasonably typical ducks exciting. However! I do know the excitement of seeing a “new” animal and ticking it off my list. My real big one back afew years ago was the Weka, I got up close and personal with that one, and of course Kiwi, Tuatara, all that NZ stuff. And their duck species too, I might add. No Takahe, or Kakapo sadly :/

    I must say though, I remain unmoved by the Adelaide Zoo’s endeavors to create excitement about their soon-to-arrive Giant Pandas. I’ve become so jaded over the subject, that I can safely say that I will not be terribly moved. It will just be another critter to tick-off my “big list of animals to see”.

  6. #6 AD
    August 27, 2009

    @ Tim- Tiritiri Matangi in Auckland Harbor- amazing, birdsong envelopes the whole island like you don’t hear on the mainland (for takahe, saddlebacks and others, but no Kakapo). Basically a recreation of the post-Maori, pre-European fauna, minus a few extinctions

  7. #7 AD
    August 27, 2009

    oops, Hauraki Gulf not “Auckland Harbor”

  8. #8 Dartian
    August 28, 2009

    Darren:

    If you said that the mystery duck from yesterday was a mallard, a weird mallard hybrid, a shoveler of some sort, or blah blah blah, then shame shame shame on you: you are a loser.

    /Hangs head in shame shame shame.

    In an attempt to save at least some face, I resort to pedantic carping:

    Meinhertzhagen

    It’s Meinertzhagen.

    There were apparently two birds in the enclosure

    Was it an open, uncovered enclosure? If so, how does the zoo prevent wild mallards from entering it and hybridising with the Meller’s ducks?

  9. #9 Tim Morris
    August 28, 2009

    AD:

    Thanks, that sounds really cool. I also got to handle some moa bones, which was a highlight.

  10. #10 windy
    August 28, 2009

    it struck me that I cannot think of a single nonhuman animal that has skin on its penis.

    The “skin” is there, it’s just in the form of a sheath in most mammals. And the normally sheathed part of the penis may be covered in mucous membrane or whatever – I assume that’s what you mean by not having skin. But I think most primates have them hanging loose like ‘ours’, like this bonobo.

  11. #11 Kevin Schreck
    August 28, 2009

    No wonder I didn’t recognize it. Thanks for the information!

  12. #12 Eike
    September 1, 2009

    I didn’t know you were into ducks Darren – I’d have thought *I* would be the only person on Earth to freak out the first time I saw _A. melleri_ (as I did, in fact).

    Well, Meller’s Ducks. Much could be said about them. Far more, however, remains unknown. It is a seriously understudied species. Do they hybridize with mallards in the wild, or do Mellers’ fight them off? They can be pretty nasty in aviculture, as they’re bigger and more territorial than mallards and do seem to have a long-term pair bond.

    Does habitat destruction – draining or conversion of swampy wetlands, mainly, as it seems – affect them significantly? They do not seem to like open lakes a lot, except to hang around and socialize outside the breeding season. And for breeding habitat, they are apparently rather picky.

    Is the population fragmented to a dangerous degree? Again, nobody seems to know. They might actually be gone from most of their historic range, but they’re (AFAIK) not even CITES-listed.

    They breed about as readily in captivity as any other dabbling duck though. Hybridization? The Cologne birds are in a fully covered enclosure. The head birdkeeper (who’s one of the coordinators of the captive breeding program) thinks they wouldn’t hybridize even in an open enclosure (a friend of his keeps Mellers’ as a hobby) because any mallard that didn’t flee would probably not survive long enough to mate.

    Konrad Lorenz apparently got hybrid offspring – but he kept one Meller’s Duck only, and IIRC it was a female. And you know how male mallards in heat are – if you can stick your penis in it, it’s fair game. Genetically, they are certainly compatible enough (non-Neoaves[*] have extremely high hybrid compatibility), but I’d believe that hybrid depression would already be easy to notice (Lorenz was somewhat nonchalant when it came to publishing actual quantitative data, but “Eurasian”-“American” mallard-group hybrids have slighly reduced vigor already).

    As regards penes, we have a) no baculum and b) a proportionally short inner foreskin (even if we still have one). Thus, when erect a proportionally larger part is covered in skin rather than in the derived mucous membrane that covers inner foreskin and glans in humans.

    [*] Presumably extending a bit down the theropod tree too. Does not translate into a significantly incxreased amount of reticulate evolution though, because the difference to Neoaves is mostly F1 hybrid viability. There, however, it is conspicuous if measured in Ma – galliform (and ratite and waterfowl, IIRC, also) hybrids are possible (though not very viable and always sterile) between lineages that separated 50 Ma ago. Passerine lineages that separated 15 Ma-ish are if anything less interfertile.

    There is not a sharp border though. Some Neoaves – Charadriiformes (which are among the basalmost crown lineages) or Paradisaeidae (which decidedly aren’t) for example – are also noted for their high incidence of natural F1 hybrids. To me, it looks as if the high hybridization capability in the more basal Neornithes is mainly due to postzygotic – i.e. genetic – factors (which were lost in the other Neoaves), whereas in hummingbirds, BoPs, NW warblers and so on, it is apomorphic, multiply convergent, and due to prezygotic – i.e. behavioral – factors (which are absent in other Neoaves).

    Cases of reticulate evolution have been noted in birds. Less than 0.01% (as a very coarse estimate) of all bird specimens used in molphyl analyses have shown strongly aberrant DNA sequences best explained by hybrid speciation. We have a case among the drepanidines but it may just as well be (and probably is) strong convergence. We have a buteo where it is the best explanation. There is (AFAIK) no known case comparable to _Rungwecebus_ (or should that be x_Rungwecebus_?) among birds (though we had the Marianas Mallard).

    Incomplete separation of lineages – species maintaining distinctness with some remnant gene flow – is by no means uncommon between mid-late Pleistocene sister species of birds. In some cases, it can persist for longer. Trying to define a strictly monophyletic “mallard” will lead to a number of interesting results.

  13. #13 Dartian
    September 2, 2009

    Eike:

    We have a case among the drepanidines but it may just as well be (and probably is) strong convergence. We have a buteo where it is the best explanation.

    Hasn’t it also been suggested that the pomarine skua Stercorarius pomarinus is of hybrid origin?

  14. #14 Darren Naish
    September 2, 2009

    Eike (comment 12): pleased to see your enthusiasm. Glyn Young, the world expert on Meller’s duck, is a regular visitor round these parts, so he might show up and answer your questions. I recall reading that Meller’s duck does not hybridise with domestic mallards in the wild, but will hybridise in captivity if the opportunity arises.

  15. #15 Dartian
    September 2, 2009

    Eike:

    The Cologne birds are in a fully covered enclosure.

    Incidentally, keeping the Meller’s ducks that way might be a good idea even if hybridisation with local mallards wasn’t an issue. There is a small breeding population of goshawks Accipiter gentilis within the city of Cologne, Germany (Würfels, 1999).

    Reference:

    Würfels, M. 1999. Ergebnisse weiterer Beobachtungen zur Populationsentwicklung des Habichts (Accipiter gentilis) im Stadtgebiet von Köln 1993–1998 und zur Rolle der Elster (Pica pica) im Nahrungsspektrum des Habichts. Charadrius 35, 20–32.

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